Electrode arrangement for electrical discharge tubes



M, TEEEELEFig ELECTRODE ARRANGEMENT FOR ELECTRICAL DISCHARGE TUBES Filed June 30 1924 mile/vim Z My, 7M

Patented May 1, 1928.

PATENT OFFICE.

MARTIN THIELEBS, OF STOCKHOLM, SWEDEN.

ELECTRODE ARRANGEMENT FOR ELECTRICAL DISCHARGE TUBES.

Application filed June 30, 1924, Serial No. 723,417, and in- Sweden July 2, 1923.

In electrical discharge tubes employed for overvoltage protection, which contain a pair of electrodes at a small mutual distance and are filled with a gas of suiiiciently low pres- 6 sure to allow the tube to discharge at only some hundred volts, it has been found difficult to suiiiciently insulate the electrodes from each other, as the corona or glow discharge has a tendency to corrode the insula- 1 tion and initiate surface discharges thereon,

whereby the insulation is still more deteriorated. Such an effect may occur even if the insulation consists of such refractory material as mica and even if the length of the surface path rises to several millimeters.

My investigation has shown that if between insulating discs close to the electrodes are interposed conducting pieces, the tendency of surface discharge is highly diminished. Such an arrangement forms the subject-matter of the present invention.

In the accompanying drawing, Fig. 1 shows the construction of the insulation between the electrodes and Fig. 2 shows a modified form thereof.

Referring to Fig. 1 (a) represents the electrodes. Next to these are placed insulating discs (6), but between the latter metal pieces (a) which of course should be totally insulated from theelectrodes. I have found that in this way the tendency of forming surface discharges are diminished. Whether this is due to the necessity of a certain minimum voltage for initiating the surface discharge, or to cooling action of the metal piece, or to still other circumstances, has not yet been determined, but my experience has shown, that if the insulation is built u in this manner, a favorable result is gained even with comparatively thin insulating discs. The discharge path may be still more subdivided by providing several dielectrically series-connected insulating layers with intermediary conducting layers.

For preventing discharge between one electrode and the terminal wire (6) Fig. 2 leading to the other at the passage through the wall (7) of the tube, which discharge may lead to cracking of the latter, each electrode may be provided, adjacent to its terminal wire (6), with a screen (d) in leading connection therewith, which takes over such a discharge and prevents it from reaching the terminal. Similar screens'in the shape of wings, borders, or the like may be arranged at other places on the electrodes, for instance for protecting the glass walls against undue heating from the are formed adjacent thereto.

Having now described my invention and the manner of its operation, what I claim 1s:--

1. In electrical discharge tubes containing a rarefied gas, electrodes connected to terminals, and insulation bet-ween said electrodes, a conductin layer interposed between layers of said insulation and insulated from any terminals.

2. In electrical discharge tubes containing a rarefied gas and electrodes, an insulating structure between said electrodes, said structure being built u of alternate layers of insulating and con ucting material.

3. In electrical discharge tubes containing rarefied gas, a pair of electrodes mechanically secured together and separated by alternate insulating and conducting layers. terminal conductors connected to, each of said electrodes, and conducting screens provided on either of said electrodes to shade its terminal conductor from the opposite electrode.

In testimony whereof I have affixed my signature.

MARTIN THIELERS. 

